Radio antennae encased in dielectric to reduce size

ABSTRACT

A radio antenna in which the length of conductor needed is appreciably reduced by the use of a compacted dielectric material as part of the antenna. Various constructions and various dielectric materials are considered.

United States Patent :wi

Wright 1 Nov. 25, I975 l 'l RADIO AN'l'l'lNN/ili ENCASED IN[)ll'lLlLtlRlC TO REDUCE. SIZE Hubert Charles Wright. Bliswurth, England[75] lnvcntm.

Plesse Handel und Investments A.(;.. lissex, England 221 Filed: June 12,1974 21; Appl No 478,890

17 ii Asslgneei [3U] Foreign Application Priority Data Aug 3t) 1971tinned Kingdom 408lU/73 2.6M 1.869 9/l952 Willoughhy. .7 343/8732,748,386 5/!956 Polydoroft 343/787 1769170 l()/l956 Clogston .7 343/87335181183 6/!970 Jones. H. 341/873 177L157 ll/l973 Slang H lit/7R7Primary Examiner-Eli Lieberman Attorney, Agenr, nr FirmScrivencr ParkerScrivener & Clarke I ABSTRACT A radio antenna in which the length ofconductor needed is appreciably reduced by the use of a compacteddielectric material as part of the antenna. Various constructions andvarious dielectric materials are considered.

7 Claims, 4 Drawing Figures US. Patent Nov. 25, 1975 3,922,684

F/G.3. F a l RADIO ANTENNAE ENCASIZI) IN DIELECTRIC TO REDUCE SIZE Thisinvention relates to radio antennae and their manufacture.

It has been found. for example in British patent specification No.27097/73 dated June 6. I973. that a workable ratio antenna can be madeif an electrical conductor is surrounded by low loss. high permittn ity.dielectric material. Such an antenna. which can be used for eithertransmission or reception. requires a smaller length of conductor for agiven frequency than does an antenna with no dielectric. A further advantage of such an antenna lies in the protection from impact and weatherwhich is afforded to the conductor by the surrounding dielectric.

A suitable dielectric material was found to be barium titanate. Thematerial was prepared in powder form. and was held around the conductorby means of a container. For a conductor of (1.3 cm radius. it was foundthat an internal container radius of about IO cm was desirable forsatisfactory functioning of the antenna.

According to the invention there is provided a radio antenna comprisingan electrical conductor in combination with dielectric material. inwhich the dielectric material is a body of compacted constituents.

The material is prepared from barium carbonate, strontium carbonate andtitanium dioxide. which are mixed together in or about the proportion of46012293 l0 parts respectively by weight. Water is added. and the mix ismilled for aproximately 1 hour. after which the mix is o\ en dried andsieved. The sieving yields a powder which is pressed into blocks ataround 2 tons per square inch. The blocks are then fired atapproximately I350C for about 2 hours. During the firing process. thecarbonates are converted into the titanates. and carbon dioxide isliberated. After the firing process. the blocks are fragmented by beingquenched from I350C into water. The fragments are ground and milleduntil a substantially uniform powder is obtained. the powder beingsubsequently dried and sieved. This powder is then compacted into rodseither hydrostatically or by extrusion. In the hydrostatic method. thepowder is subjected to a pressure of 33 tons per square inch and firedat [200C In the extrusion method. the powder is mixed with polyvinylalcohol.

Rods prepared in this way can be bored to receive a conductor. For aconductor of radius 0.3 cm. a rod radius of less than It) cm isacceptable.

Various antenna constructions are possible. Four possible constructionsare shown in cross section in FIGS. l4 respectively of the accompanyingdrawings.

In each example signals are conveyed to or from the antenna by a coaxialcable. comprising a core I and a sleeve 2. In FIGS. I. 2, 3 the core Iis joined to a conducting rod 3 of the antenna. The rod 3 is located ina central bore of a cylinder 4 of compacted dielectric material.conveniently made in the manner just described. The cable sleeve 2 isconnected: in FIG. I to a conductive ground plate 5 extending at rightangles to the rod 3: in FIG. 2 to a conductive annulus 6 encircling thecore I where the core joins the rod 3: and in FIG. 3 by a wire 7 to aconductive band 8 encircling the cylinder 4 near its mid point. In theembodiment of FIG. 4, the cylinder 10 of dielectric material is solidand has a conductive disc at each end as shown at II. I2. The cable coreI is joined directly to the disc II. and the sleeve 2 is joined by awire [3 to the disc I2.

Using a compacted mixture of barium strontium titanate as a dielectricin a reception antenna. it has been found possible to make the lengthofthe rod 3 equal to one eighth of the length required for an antennawith no dielectric. the frequency employed being (183MHz. At a frequencyof 90MH2. the fraction was one fifth.

When used as for transmitting in the band 400-500MH2. a conductive rodsurrounded by dielectric showed a gain of Sdb compared with a rod ofequal length having no dielectric.

Alternative dielectric materials can be prepared by mixing (a) lanthanumoxide. magnesium carbonate and titanium oxide in or about the proportionof 25:72:25 parts respectively by weight; and (b) calcium oxide. bismuthoxide and titanium oxide in or about the proportion of 23:3l:46 partsrespectively by weight. With mixture (at) the constituents of theresulting dielectric material are lanthanum titanate and magnesiumtitanate; and with mixture (b) calcium titanate and bismuth titanate.

It is to be understood that the foregoing description of specificexamples of this invention is made by way of example only and is not tobe considered as a limitation in its scope.

What is claimed is:

l. A radio antenna comprising an electrical conductor in combinationwith low-loss high permittivity dielectric material formed of a mixtureof titanates compacted under pressure to form a rigid structure. saiddielectric matcrial being a single cylindrical body of uniform diameterwith a central hold bored therein to receive the electrical conductoralong the length thereof.

2. An antenna as claimed in claim I in which the constituents are bariumtitanate and strontium titanate.

3. An antenna claimed in claim I in which the constituents are lanthanumtitanate and magnesium titanate.

4. An antenna as claimed in claim I in which the constituents arecalcium titanate and bismuth titanate.

5. An antenna as claimed in claim I which includes a conductive groundplate extending at right angles to the cylinder at one end of thecylinder.

6. An antenna as claimed in claim I which includes a conductive annulusat one end of the cylinder.

7. An antenna as claimed in claim I which includes a conductive bandencircling the cylinder about the midpoint of the cylinder.

1. A radio antenna comprising an electrical conductor in combinationwith low-loss high permittivity dielectric material formed of a mixtureof titanates compacted under pressure to form a rigid structure, saiddielectric material being a single cylindrical body of uniform diameterwith a central hold bored therein to receive the electrical conductoralong the length thereof.
 2. An antenna as claimed in claim 1 in whichthe constituents are barium titanate and strontium titanate.
 3. Anantenna as claimed in claim 1 in which the constituents are lanthanumtitanate and magnesium titanate.
 4. An antenna as claimed in claim 1 inwhich the constituents are calcium titanate and bismuth titanate.
 5. Anantenna as claimed in claim 1 which includes a conductive ground plateextending at right angles to the cylinder at one end of the cylinder. 6.An antenna as claimed in claim 1 which includes a conductive annulus atone end of the cylinder.
 7. An antenna as claimed in claim 1 whichincludes a conductive band encircling the cylinder about the mid-pointof the cylinder.